1. Field of Use
The present invention relates to data processing systems and more particularly to timing apparatus for measuring the required time intervals for such data processing systems.
2. Prior Art
In many sophisticated data processing systems, it is important to be able to control efficiently the time out of events to ensure proper utilization of system's resources (e.g. processors, memory space and input/output devices by being able to detect the completion of such events). For example, the central processor normally employs an interval timer which enables it to keep track of the time of day and to interrupt periodically as required. Thus, this allows for the performance of functions such as the time out of events (watchdog timer operations), the polling of communication networks on a regular basis and time of day recording.
In many prior art systems, it is encumbent upon the processor to respond to a time out condition within a minimum period of time after receipt of a timer interrupt. The reason is that waiting can result in the read out of inaccurate time information. Accordingly, the processor is required to interrupt normal processing to respond immediately to each timer produced interrupt. In addition to increasing processing overhead, this can result in other deficiencies particularly where the processor is performing input/output operations.
Accordingly, it is a primary object of the present invention to provide a timer which has high resolution.
It is a more specific object of the present invention to provide a timer which requires low overhead in servicing without sacrificing accuracy in the time dependent information it provides.
It is still a further object of the present invention to provide a timer arrangement which facilitates the performance of functions relating to input/output operations.